In a total of 3 places in the 4 principle Nikayas an argument is given to the effect that the self is a fiction.
“But self and what belongs to a self are not acknowledged as a genuine fact. This being so, is not the following a totally foolish teaching:
“Attani ca, bhikkhave, attaniye ca saccato thetato anupalabbhamāne, yampi taṁ diṭṭhiṭṭhānaṁ:
‘The self and the cosmos are one and the same. After death I will be permanent, everlasting, eternal, imperishable, and will last forever and ever’?”
‘so loko so attā, so pecca bhavissāmi nicco dhuvo sassato avipariṇāmadhammo, sassatisamaṁ tatheva ṭhassāmī’ti— nanāyaṁ, bhikkhave, kevalo paripūro bāladhammo”ti?
“In that case, Reverend Yamaka, since you don’t acknowledge the Realized One as a genuine fact in the present life, is it appropriate to declare:
“Ettha ca te, āvuso yamaka, diṭṭheva dhamme saccato thetato tathāgate anupalabbhiyamāne, kallaṁ nu te taṁ veyyākaraṇaṁ:
‘As I understand the Buddha’s teaching, a mendicant who has ended the defilements is annihilated and destroyed when their body breaks up, and doesn’t exist after death.’?”
‘tathāhaṁ bhagavatā dhammaṁ desitaṁ ājānāmi, yathā khīṇāsavo bhikkhu kāyassa bhedā ucchijjati vinassati, na hoti paraṁ maraṇā’”ti?
“In that case, Anurādha, since you don’t acknowledge the Realized One as a genuine fact in the present life, is it appropriate to declare:
“Ettha ca te, anurādha, diṭṭheva dhamme saccato thetato tathāgate anupalabbhiyamāne kallaṁ nu te taṁ veyyākaraṇaṁ
‘Reverends, when a Realized One is describing a Realized One—a supreme person, highest of people, who has reached the highest point—they describe them other than these four ways:
yo so, āvuso, tathāgato uttamapuriso paramapuriso paramapattipatto, taṁ tathāgato aññatra imehi catūhi ṭhānehi paññāpayamāno paññāpeti:
After death, a Realized One exists, or doesn’t exist, or both exists and doesn’t exist, or neither exists nor doesn’t exist’?”
‘hoti tathāgato paraṁ maraṇā’ti vā …pe… ‘neva hoti na na hoti tathāgato paraṁ maraṇā’ti vā”ti?
“No hetaṁ, bhante”.
The parallels in all three cases omit this argument.
Outside of the above 3 examples, the “not a genuine fact” argument is not given in the 4 principle Nikayas, and in each case the argument is missing from the Agama parallel.